class_docstr: A highly optimized equivalent of lambda x: Entmax15([x, 0]) 
code: def forward(ctx, input):
      output = Entmoid15._forward(input)
      ctx.save_for_backward(output)
      return output
  
imports: from torch import nn
  from torch.autograd import Function
  import torch.nn.functional
  import torch
label_desc: Use image node_id 1 for calling the Entmoid15 obj's underlying member method code with example usage: obj.forward(ctx, input) and returns: output